The laminar distribution of retinal fibers in the dorsal lateral geniculate nucleus of the cat: A new interpretation

Abstract

The cell laminae of the lateral geniculate nucleus have been studied in relation to the retinogeniculate degeneration shown by the Nauta method. In agreement with previous accounts laminae A and A1 have been shown to receive contralateral and homolateral inputs respectively. However, ventral to lamina A1 three laminae have been defined. Lamina “C” contains large cells and receives coarse contralateral fibers, lamina “C1” contains smaller cells and receives fine homolateral fibers, while lamina “C2,” which consists of small cells next to the optic tract contains many fibers passing through to other laminae but shows no particular concentration of pericellular degeneration. The precise relationship between fiber degeneration and cytoarchitectonic borders can be seen only in Nauta sections that have been counterstained by a Nissl method. Such material provides no evidence of any zone where homolateral and contralateral fibers overlap. Between laminae A and A1, and A1 and C there are narrow, relatively cell free zones, which, in many parts of the nucleus, receive no significant retinogeniculate input. The fiber degeneration appears earliest in the peripheral parts of laminea A and A1, the homolateral degeneration slightly preceding the contralateral degeneration on the third day. The degeneration in the central parts of these laminae appears about 24 hours later and is never as dense. The fine fibers in lamina C1 do not show degeneration clearly until the sixth day.